drm/amdgpu: add debugfs support for VM pagetable per client

Add a debugfs file under the client directory which shares
the root page table base address of the VM.

This address could be used to dump the pagetable for debug
memory issues.

Signed-off-by: Sunil Khatri <sunil.khatri@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/r/20250704075548.1549849-4-sunil.khatri@amd.com


Signed-off-by: Christian König <christian.koenig@amd.com>